On October 23rd, 2014, we updated our
By continuing to use LinkedIn’s SlideShare service, you agree to the revised terms, so please take a few minutes to review them.
Matter andChange P Squires General Chemistry 2005-2006
Observing Chemical Change• Open book to page 55 and conduct Discovery Lab • (50 pts)
Properties of Matter•What is a substance?• Physical Properties• Chemical Properties
Physical StatesSolid What are some Liquid characteristics of each? Gas Plasma
Give the physical state of each of these: 1. Silver Solid 2. Gasoline Liquid 3. Helium Gas 4. Rubbing alcohol Liquid 5. Air Gas 6. Glass Solid or liquid 7. Lightning Plasma
Physical Changes • Physical changes only involve changes in state or appearance.• What are some examples of physical change?
Catch words for Physical Change• Boil •Split• Freeze •Grind• Melt •Cut• Condense •Crush• Break •Bend
Chemical Changes• Chemical changes and chemical properties always produce new substances.
Chemical or physical change ???• Food spoiling Chemical• Nail rusting Chemical• Oil burning Chemical• Sugar dissolving Physical• Water boiling Physical• Firefly flashing Chemical• Egg cooking Chemical• Snowflake melting Physical
Percent massPercent mass (%) = mass of element_ x 100 mass of compound
Calculations1. A 78.0 g sample of an unknown compound contains 12.4 g of hydrogen. What is the percent by mass of hydrogen in the compound?2. If 1.0 g of hydrogen reacts completely with 19.0 g of fluorine, what is the percent by mass of hydrogen in the compound that is formed?
Pure Substances• Elements are the building blocks of matter.• Atoms are the smallest part of an element.
Mixtures… do not have a definite composition… are either heterogeneous,with clearly visible components… or homogeneous, which are uniform in appearance
Solutions• Solutions are homogeneous mixtures containing a solute which is dissolved in a solvent.
How would you separate the following?Aluminum filings and iron filings? Saw dust and sand? Salt and powdered charcoal? Water and alcohol?
Elements• A pure substance that can not be separated into simpler substance by physical or chemical means.
Compounds• A combination of two or more different elements that are combined chemically.• What are some examples of compounds?
The Law of Conservation of MassMatter can neither be created or destroyed during a chemical reaction.
Law of Definite Proportions Elements comprisecompounds in definite proportions by mass.
Law of Multiple Proportions When different compounds are formed, they combine in whole number ratios. H2O H2O2
ChemLab• Read and complete ChemLab page 78. (100 points) • Answer Questions at end: Analyze and Conclude.
Structure of the Atom
Part of the Atom• Electron• Proton What charge does each have?• Neutron Where are they found? Which ones make up the mass of the atom? Which ones make up the size of the atom?
How Do Atoms Differ? •Atomic Number •Atomic Mass
Element Atomic Protons Electrons Atomic Number Mass He 2 Pb 82 8 30
Mass Number Number of neutrons =mass number – atomic number
Isotopes ……of the same element have thesame number of protons andelectrons but different numbers ofneutrons. Therefore, isotopes of the same element have different masses.
Symbols for Isotopes Mass numberA is the A Symbol Esymbolfor mass Z of Elementnumber Z is the symbol for Atomic number atomic number
MiniLab• Do modeling isotope lab on page 102.
Light and Energy• Frequency = f or f with units of Hertz (Hz)• Wavelength = λ with units of meters (m)
What is the relationshipbetween frequency and wavelength?
For electromagneticenergy, the equation is: c = fλ c is the speed of light c = 3.00 x 10 m/sec 8
Electromagnetic Spectrum• Electromagnetic waves carry energy. • Light is part of theelectromagnetic spectrum
The Electromagnetic Spectrumgamma rays microwaves visible light ultraviolet infraredX-rays radar radio TV Shorter wavelength Longer wavelength Higher frequency Lower frequency Higher energy Lower energy
gamma rays X-rays 400 nm ultraviolet visible light infrared microwavesIncreasing energy radar TV 700 nm radio The Electromagnetic Spectrum
The visible spectrum wasdiscovered by … Dr. Roy G. BivRed Orange Yellow Green Blue Indigo Violet 700 nm 400 nm Lower energy Higher energy
Niels BohrBohr said that electrons could exist only in certain discrete energy levels … … and that electrons can only change energy levels when they absorb or give off a certain amount of energy. (1913)
Hydrogen atomDiscrete energy levels for electronselectron nucleus
Hydrogen atomElectrons can exist in this orbit,
Hydrogen atom…or in this orbit,
Hydrogen atom…or inthis orbit,
Hydrogen atom…but not in between the orbits.
Hydrogen atomUnless the electron isabsorbing energy, or …Giving off energy
When high voltage is connected to the hydrogen discharge tube, a bluish light is given off.When observed through a diffraction grating, specific lines of color are observed.
The electron in a hydrogen atom gains energy from the electricity passing thru the tube and …… the electron moves up to a higher energy level.
The electron in the excited state is “unstable”.The electron drops to a lower energy level, and …… gives off light of a certain energy and wavelength.
HydrogenThe electronabsorbs atomenergy and … ener g y
Hydrogen atom …the electron is elevated to the nextenergy level
Hydrogen atom The electron is unstable and “wants” toreturn to a lower energy level
Hydrogen atomLight of aparticularwavelengthis given off
“Regardless of it’s shortcomings and themodifications that were laterapplied, Bohr’s model of the atom was the firstsuccessful attempt to makethe internal structure of the atom agree with spectroscopic data.” Asimov, 1964
QuantumMechanical Model of the Atom1. A small, dense positively charged nucleus which contains protons and neutrons.2. Electrons which exist outside of the nucleus at … – various distances from the nucleus, and at … – various energy levels.
The Electrons3. The electrons can have both a mass, as does matter, and a wavelength, as does light energy.4. The electrons themselves are not little solid spheres in orbit around the nucleus, but exist as a “fog” of half- energy, half-matter. The electrons can behave as either matter or energy, depending on the experiment.
Energy Levels5. Based on the ideas of Bohr, the electrons are located … – … in major energy levels, – … in energy sublevels within major energy levels, – … in orbitals within each sublevel.